Overkill Solar 120A 4s 12V BMS, Instruction Manual

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Heavy-duty >12” zip ties​ ​ (Optional; for mounting the BMS to the battery pack)
2.2.2 Gather Tools
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Ratcheting insulated terminal crimper​ ​ (needed for crimping insulated ring terminals to the balance
leads)​ . Most ratcheting crimpers will be rated for 10-22 AWG, and have three separate crimping
zones: red, blue, and yellow.
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Hammer lug crimper​ or ​hydraulic crimper​ ​ (needed for crimping the heavy-gauge ring terminals)
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Cable-stripping knife​ ​ (needed for stripping large-gauge wire) ​ A razor blade or a knife are acceptable
substitutes, but aren’t as safe to use.
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Wire strippers​, capable of stripping 26 AWG, Klein Tools 11057 or similar ​ (needed to strip the balance
leads)
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Wire shears​, Klein Tools 63050 or similar ​ (needed to cut the large-gauge cables)
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Socket and wrench set​ ​ (needed to tighten the battery lugs). ​ The recommended Overkill Solar 100Ah
LiFePO4 cells come with 17mm nylon-insert locking nuts.
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A ​phone, tablet with Bluetooth, or a laptop with USB​ ​ (Optional; Can be used for programming the
BMS. Programming is not needed for common configurations)​ . See ​ Appendix A​ for recommended
parameters, and ​ Appendix E​ for installation and usage.
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A ​felt-tip pen​ or ​label maker​ for labelling the cells and balance leads
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A ​lab CC-CV power supply​ capable of around 10 amps or ​LiFePO4 battery charger​ capable of
charging a single cell ​
(one or the other is needed for top-balancing the cells)​ . Note that if you ordered
the cells from Overkill Solar 100Ah LiFePO4 cells, and they were all ordered at the same time, the
top-balancing step can be skipped because it was done before they were shipped to you. The top
balancing procedure is covered in ​
Section 2.3​ .
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A ​handheld voltmeter​ for troubleshooting and BMS calibration. If you plan to calibrate your BMS, the
voltmeter needs to be accurate to at least 1 millivolt. If you use a cheap or badly-calibrated voltmeter,
you will only make your calibration worse.
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A ​clamp-style current meter​ (optional; but required for BMS calibration). Most handheld multimeters
will only measure DC current up to 10 amps; these are not sufficient. We recommend a clamp meter
capable of measuring DC current at greater than 100 amps, at an accuracy better than +/- 2.0%. If
purchasing a new clamp meter, always make 100% sure that it will measure DC current. Cheaper
models only measure AC current.
2.3 Top Balancing
Before the battery pack is assembled, lithium battery cells must be top-balanced, if the factory or vendor did
not do so before shipment ​
[1]​ . This is an essential step, and should never be skipped. If you have been told
differently, or don’t believe us, please read ​ Appendix C​ , where we explain why.
[1]​ Overkill Solar 100Ah LiFePO4 cells are shipped top-balanced. If you purchased all cells at the same time,
from Overkill Solar, then there you can skip this section.
With that out of the way, it’s time to top-balance the battery cells.
Note that this process will take some time. It could take a few days, depending on how many cells you plan on
using, and where the state of charge was in each cell before they shipped. Typically cells are shipped at lower
than 50% charge, but don’t count on this. Assuming your charger or power supply is rated at 10 amps, it will